Vehicle state estimation device, vehicle state estimation method, and non-transitory computer-readable storage medium

Abstract

The present invention provides a vehicle state estimation device, a vehicle state estimation method, and a non-transitory computer-readable storage medium. The vehicle state estimation device is used in a vehicle equipped with an inertial measurement sensor and a wheel speed sensor, and includes: a vehicle state estimation unit that estimates the vehicle state, including the vehicle speed, based on the acceleration and angular velocity obtained by the inertial measurement sensor and the wheel speed obtained by the wheel speed sensor; and a determination unit that determines whether the wheel is slipping. The vehicle state estimation unit estimates the steady-state vehicle speed based on the wheel speed and calculates the instantaneous vehicle speed by time integration based on the acceleration and angular velocity. When the wheel is slipping, the estimation unit determines that the estimated value of the vehicle speed is close to the instantaneous vehicle speed, and when the wheel is not slipping, the vehicle state estimation unit determines that the estimated value of the vehicle speed is close to the steady-state vehicle speed.

Description

Technical Field

[0001] The present invention relates to a vehicle state estimation device, a vehicle state estimation method, and a vehicle state estimation program (stored in a non-transitory computer-readable storage medium) for estimating a vehicle's driving state (particularly, a vehicle's speed and attitude angle). Background Art

[0002] A vehicle driving state estimation device is known that estimates the vehicle driving state based on a two-wheel model consisting of an equation describing the translational motion of the vehicle's center of gravity and an equation describing the vehicle's rotational motion (e.g., JP2007-106273A). The vehicle driving state estimation device disclosed in JP2007-106273A estimates the vehicle's sideslip angle, road friction coefficient, and other information as the vehicle's driving state based on information from a steering angle sensor, a yaw rate sensor, a lateral acceleration sensor, and a vehicle speed sensor.

[0003] As described in JP2007-106273A, vehicle states, such as vehicle velocity and attitude angle, are generally described by differential equations of motion. Therefore, numerical integration of the equations of motion is necessary to obtain the vehicle state. However, since numerical integration involves errors, the accuracy of vehicle state estimation degrades over time. Summary of the Invention

[0004] In view of the above background, the main purpose of the present invention is to provide a vehicle state estimation device, a vehicle state estimation method and a vehicle state estimation program (stored in a non-temporary computer-readable storage medium) for estimating the vehicle state, which can improve the estimation accuracy of the vehicle state compared to the case where the vehicle state estimation is always obtained through numerical integration.

[0005] In order to achieve the above-mentioned purpose, one aspect of the present invention provides a vehicle state estimation device 1, which is configured to be installed in a vehicle S to estimate the vehicle state including the vehicle speed, wherein the vehicle is provided with an inertial measurement sensor 5 for obtaining acceleration and angular velocity and a wheel speed sensor 9 for obtaining wheel speed, and the vehicle state estimation device includes: a vehicle state estimation unit 31, which estimates the vehicle state based on the acceleration and angular velocity obtained by the inertial measurement sensor and the wheel speed obtained by the wheel speed sensor; and a determination unit 41, which determines whether the wheel is in a slipping state, wherein the vehicle state estimation unit estimates a steady-state vehicle speed based on the wheel speed and calculates an instantaneous vehicle speed by time integration based on the acceleration and the angular velocity, and when the wheel is in the slipping state, the vehicle state estimation unit determines that the estimated value of the vehicle speed is close to the instantaneous vehicle speed, and when the wheel is not in the slipping state, the vehicle state estimation unit determines that the estimated value of the vehicle speed is close to the steady-state vehicle speed.

[0006] When the wheels are not in a slipping state, the vehicle speed obtained from the wheel speed is close to the true value. On the other hand, when the wheels are in a slipping state, the vehicle speed obtained from the wheel speed is far from the true value and the error is large.

[0007] According to the above aspect, when the wheels are not in a slipping state, the estimated value of the vehicle speed is determined to be close to the steady-state vehicle speed estimated based on the wheel speed acquired by the wheel speed sensor. Therefore, the estimation accuracy of the vehicle speed can be improved compared to a case where the estimated value of the vehicle speed is determined to be close to the instantaneous vehicle speed obtained by numerical integration of the motion equation. In addition, when the wheels are in a slipping state, the estimated value of the vehicle speed is determined to be close to the instantaneous vehicle speed. Therefore, the estimation accuracy can be improved compared to a case where the estimated value is determined to be close to the steady-state vehicle speed calculated based on the wheel speed.

[0008] In the above aspects, preferably, the vehicle state includes the attitude angle of the vehicle, and the vehicle state estimation unit calculates the steady-state attitude angle based on the gravity direction estimated using the wheel speed and the acceleration obtained by the inertial measurement sensor, and calculates the instantaneous attitude angle by time integrating the angular velocity obtained by the inertial measurement sensor, and when the wheel is in the slipping state, the vehicle state estimation unit determines that the estimated value of the attitude angle is close to the instantaneous attitude angle, and when the wheel is not in the slipping state, the vehicle state estimation unit determines that the estimated value of the attitude angle is close to the steady-state attitude angle.

[0009] When the wheels are not slipping, the vehicle velocity obtained from the wheel speed is close to the true value. Therefore, the steady-state attitude angle calculated based on the wheel speed, acceleration obtained by the inertial measurement sensor, and other factors is close to the true value of the attitude angle. On the other hand, when the wheels are slipping, the vehicle velocity obtained from the wheel speed deviates from the true value. Therefore, the instantaneous attitude angle obtained by numerical integration of the angular velocity is closer to the true value of the attitude angle than the steady-state attitude angle calculated from the wheel speed and other factors.

[0010] According to the above aspect, when the wheel is not in a slipping state, the estimated value of the attitude angle is determined to be close to the steady-state attitude angle, thereby improving the estimation accuracy compared to a case where the estimated value is determined to be close to the instantaneous attitude angle. When the wheel is in a slipping state, the attitude angle is determined to be close to the instantaneous attitude angle, thereby improving the estimation accuracy compared to a case where the estimated value is determined to be close to the steady-state attitude angle.

[0011] In the above aspects, preferably, the vehicle state estimation unit estimates the vehicle velocity and the attitude angle based on the following equations: a rate observer equation, which indicates that the relative derivative of the vehicle velocity is equal to the sum of the acceleration due to gravity, the acceleration obtained by the inertial measurement sensor, the vector product of the estimated value of the vehicle velocity and the angular velocity obtained by the inertial measurement sensor, and a feedback term for providing feedback at a prescribed acceleration gain to make the vehicle velocity approach the steady-state vehicle velocity; and an attitude angle observation equation, which indicates that the time derivative of the attitude angle is equal to the sum of the instantaneous attitude angle and a feedback term for providing feedback at a prescribed attitude angle gain to make the attitude angle approach the steady-state attitude angle.

[0012] According to this aspect, because neither the velocity observer equation nor the attitude angle observation equation includes the vehicle's mass or friction coefficient, the vehicle's velocity and attitude angle can be calculated without requiring the vehicle's mass and friction coefficient. Therefore, vehicle state estimation can be achieved that is independent of the vehicle's usage status.

[0013] In the above aspect, preferably, the vehicle state estimation unit makes the acceleration gain and the attitude angle gain smaller when the wheel is in the slipping state than when the wheel is not in the slipping state.

[0014] According to this aspect, when the wheels are not in a slipping state, the estimated value of the vehicle speed can be determined to be a value close to the steady-state vehicle speed, and the estimated value of the attitude angle can be determined to be a value close to the steady-state attitude angle. When the wheels are in a slipping state, the estimated value of the vehicle speed can be determined to be a value close to the instantaneous vehicle speed, and the estimated value of the attitude angle can be determined to be a value close to the instantaneous attitude angle.

[0015] In the above aspect, preferably, the determination unit includes at least one of an anti-lock braking system 43 and a traction control system 45 .

[0016] According to this aspect, it is possible to conveniently know whether the wheel is in a slipping state based on activation of the anti-lock braking system or the traction control system.

[0017] In order to achieve the above purpose, another aspect of the present invention provides a vehicle state estimation method, which is used to estimate the vehicle state including the vehicle speed of a vehicle S, which is provided with an inertial measurement sensor 5 for obtaining acceleration and angular velocity and a wheel speed sensor 9 for obtaining wheel speed. The vehicle state estimation method includes the following steps: determining whether the wheel is in a slipping state; estimating the steady-state vehicle speed based on the wheel speed; calculating the instantaneous vehicle speed through time integration based on the acceleration and the angular velocity; and when the wheel is in the slipping state, determining that the estimated value of the vehicle speed is close to the instantaneous vehicle speed, and when the wheel is not in the slipping state, determining that the estimated value of the vehicle speed is close to the steady-state vehicle speed.

[0018] According to this aspect, when the wheels are not in a slipping state, the estimated value of the vehicle speed is determined to be close to the steady-state vehicle speed estimated based on the wheel speeds acquired by the wheel speed sensors. Therefore, the estimation accuracy of the vehicle speed can be improved compared to a case where the estimated value of the vehicle speed is determined to be close to the instantaneous vehicle speed obtained by numerical integration of the equation of motion. Furthermore, when the wheels are in a slipping state, the estimated value of the vehicle speed is determined to be close to the instantaneous vehicle speed. Therefore, the estimation accuracy can be improved compared to a case where the estimated value is determined to be close to the steady-state vehicle speed calculated based on the wheel speeds.

[0019] In the above aspects, preferably, the vehicle state includes an attitude angle of the vehicle, and the vehicle state estimation method includes the following steps: calculating a steady-state attitude angle based on the gravity direction estimated using the wheel speed and the acceleration obtained by the inertial measurement sensor; calculating an instantaneous attitude angle by time integrating the angular velocity obtained by the inertial measurement sensor; and when the wheel is in the slipping state, determining that the estimated value of the attitude angle is close to the instantaneous attitude angle, and when the wheel is not in the slipping state, determining that the estimated value of the attitude angle is close to the steady-state attitude angle.

[0020] According to this aspect, when the wheel is not in a slipping state, the estimated value of the attitude angle is determined to be close to the steady-state attitude angle, thereby improving estimation accuracy compared to a case where the estimated value is determined to be close to the instantaneous attitude angle. When the wheel is in a slipping state, the attitude angle is determined to be close to the instantaneous attitude angle, thereby improving estimation accuracy compared to a case where the estimated value is determined to be close to the steady-state attitude angle.

[0021] In the above aspects, preferably, the vehicle state estimation method estimates the vehicle velocity and the attitude angle based on the following equations: a rate observer equation, the rate observer equation indicates that the relative derivative of the vehicle velocity is equal to the sum of the acceleration due to gravity, the acceleration obtained by the inertial measurement sensor, the vector product of the estimated value of the vehicle velocity and the angular velocity obtained by the inertial measurement sensor, and a feedback term for providing feedback at a prescribed acceleration gain to make the vehicle velocity approach the steady-state vehicle velocity; and an attitude angle observation equation, the attitude angle observation equation indicates that the time derivative of the attitude angle is equal to the sum of the instantaneous attitude angle and the feedback term for providing feedback at a prescribed attitude angle gain to make the attitude angle approach the steady-state attitude angle, and the method makes the acceleration gain and the attitude angle gain when the wheel is in the slipping state smaller than when the wheel is not in the slipping state.

[0022] According to this aspect, since neither the vehicle's mass nor the friction coefficient is included in the velocity observer equation nor the attitude angle observer equation, the vehicle's velocity and attitude angle can be calculated without requiring the vehicle's mass and friction coefficient. Consequently, vehicle state estimation can be achieved that is independent of the vehicle's usage status.

[0023] In addition, when the wheels are not in a slipping state, the estimated value of the vehicle speed can be determined to be a value close to the steady-state vehicle speed, and the estimated value of the attitude angle can be determined to be a value close to the steady-state attitude angle. When the wheels are in a slipping state, the estimated value of the vehicle speed can be determined to be a value close to the instantaneous vehicle speed, and the estimated value of the attitude angle can be determined to be a value close to the instantaneous attitude angle.

[0024] In order to achieve the above objectives, another aspect of the present invention provides a non-transitory storage medium, which includes a stored program, wherein the stored program performs the above method when executed by a processor.

[0025] According to this aspect, the effects described above with respect to the method according to aspects of the present invention can also be provided.

[0026] According to the above arrangement, a vehicle state estimation device and a vehicle state estimation method as well as a vehicle state estimation program (stored in a non-temporary computer-readable storage medium) for estimating the vehicle state can be provided, which can improve the estimation accuracy of the vehicle state compared to the case where the estimated value of the vehicle state is always obtained through digital integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a perspective view of a vehicle equipped with a vehicle state estimation device according to an embodiment of the present invention;

[0028] Figure 2is a functional configuration diagram of a vehicle state estimation device;

[0029] Figure 3 is a flowchart of an abnormality determination process; and

[0030] Figure 4A and Figure 4B It is a graph showing the true value of the lateral velocity when the vehicle is traveling without slipping (grip driving) and when the vehicle is slipping (slipping driving), the steady-state vehicle velocity, the instantaneous vehicle velocity and the estimated value of the vehicle velocity (estimated vehicle velocity), respectively. DETAILED DESCRIPTION

[0031] Hereinafter, one embodiment of a vehicle state estimation device, a vehicle state estimation method, and a vehicle state estimation program according to the present invention will be described with reference to the accompanying drawings.

[0032] like Figure 2 As shown in FIG, a vehicle state estimation device 1 according to an embodiment of the present invention is provided in a vehicle S that can travel autonomously.

[0033] Hereinafter, for convenience of explanation, a coordinate system (eg, a coordinate system fixed to a road surface to have an X-axis and a Y-axis extending horizontally in two directions orthogonal to each other and a Z-axis extending vertically upward) is referred to. Figure 1 ) will be referred to as the fixed coordinate system (also called the inertial coordinate system).

[0034] like Figure 2 As shown in FIG, a vehicle S is provided with a vehicle control system 3 for controlling the behavior of the vehicle S so that the vehicle S can travel autonomously. The vehicle control system 3 includes: two inertial measurement sensors 5 and 7; a wheel speed sensor 9; an external environment recognition device (not shown); a steering and acceleration / deceleration device 13; a human-machine interface (HMI) 15; and a control device 17.

[0035] The inertial measurement sensors 5 and 7 are fixed to the vehicle body. One of the inertial measurement sensors 5 and 7 (in this embodiment, the main inertial measurement sensor 5) is a so-called six-axis inertial measurement sensor and detects acceleration G along three axes. sens and angular velocities ω around the three axes.

[0036] The main inertial measurement sensor 5 measures the acceleration G sens The main inertial measurement sensor 5 outputs an acceleration G with respect to a coordinate system having an X axis, a Y axis, and a Z axis and fixed to the main inertial measurement sensor 5 (ie, fixed to the vehicle body). sens. Hereinafter, this coordinate system will be referred to as the acceleration coordinate system. Note that the main inertial measurement sensor 5 is fixed to the vehicle body so that the positive direction of the x-axis coincides with the forward direction of the vehicle body, the positive direction of the y-axis coincides with the left direction of the vehicle body, and the positive direction of the z-axis coincides with the upward direction of the vehicle body. That is, the x-axis is set to extend in the front-to-rear direction of the vehicle body, the y-axis is set to extend in the lateral direction of the vehicle body, and the z-axis is set to extend in the vertical direction of the vehicle body. Below, for ease of explanation, the origin of the acceleration coordinate system is located at the position where the main inertial measurement sensor 5 is set.

[0037] In this embodiment, the main inertial measurement sensor 5 includes three housings held by the vehicle body, each housing having a detection electrode. Each housing has a counterweight housed therein, such that the counterweight is held in the housing in one of the x-axis, y-axis, and z-axis directions via two springs. The main inertial measurement sensor 5 measures the inertial force applied to each counterweight by detecting changes in the electrostatic capacitance between the counterweight and the corresponding detection electrode. The inertial force is divided by the mass of the counterweight, and the direction (or sign) of the value obtained by the division is reversed to calculate the acceleration and output the acceleration. Note that the main inertial measurement sensor 5 is not limited to this configuration and can be embodied using a piezoelectric element, for example, which generates a voltage based on the deformation when deformed by the inertial force. In this case, the main inertial measurement sensor 5 can obtain the inertial force by detecting the voltage generated by the piezoelectric element, and calculate and output the acceleration based on the inertial force.

[0038] If the acceleration G output from the main inertial measurement sensor 5 sens The x component, y component and z component of G are respectively sensx , G sensy , G sensz , then the acceleration G acting on the vehicle S in the fixed coordinate system (G = ΣF / m, where ΣF represents the sum of forces acting on the vehicle S other than gravity, and m represents the mass of the vehicle S) satisfies the following formula (1):

[0039]

[0040] Please note that i, j and k represent the unit vectors in the x-axis, y-axis and z-axis directions in the acceleration coordinate system, respectively, and Gv represents the acceleration due to gravity. Formula (1) shows that due to the acceleration due to gravity Gv (G sens =G-Gv), the acceleration G measured by the main inertial measurement sensor 5 sens There is a deviation from the acceleration G acting on the vehicle S, so it is necessary to correct the acceleration G measured by the main inertial measurement sensor 5 while taking into account the influence of the gravitational acceleration Gv. sens , to obtain the acceleration G acting on the vehicle S.

[0041] The deviation due to the gravitational acceleration Gv can be explained as follows. When the sum of the forces applied to the vehicle S is 0 and the vehicle S is stopped, the acceleration G output from the main inertial measurement sensor 5 is sens =Equal to -1 times the gravitational acceleration Gv. This is because the main inertial measurement sensor 5 calculates acceleration based on inertial force and cannot distinguish the gravity acting on the counterweight from the inertial force. In other words, the main inertial measurement sensor 5 interprets the vertically downward gravity acting on the counterweight as an inertial force caused by the vertically upward acceleration of the housing (vehicle body) and outputs acceleration accordingly. Correction that takes into account the influence of gravitational acceleration Gv is correction that accounts for the influence of the acceleration calculated by the main inertial measurement sensor 5 based on inertial force.

[0042] The acceleration G measured by the primary inertial measurement sensor 5 sens The main inertial measurement sensor 5 outputs the angular velocity ω relative to the acceleration coordinate system, which is related to the acceleration G sens Similarly, the x component of the angular velocity ω corresponds to the roll rate, the y component of the angular velocity ω corresponds to the pitch rate, and the z component of the angular velocity ω corresponds to the yaw rate. The main inertial measurement sensor 5 acquires the angular velocity ω and the acceleration G sens Output to the control device 17.

[0043] The other of the inertial measurement sensors 5 and 7 (hereinafter referred to as the auxiliary inertial measurement sensor 7) is a so-called three-axis inertial measurement sensor, and acquires the acceleration G′ in the x-axis direction in a fixed coordinate system based on a similar principle to the main inertial measurement sensor 5. sensx , acceleration G' in the y-axis direction sensy and the angular velocity ω' around the z axis z , and output them to the control device 17.

[0044] For example, the auxiliary inertial measurement sensor 7 may be a sensor provided in a device not specifically designed for the purpose of estimating the vehicle state, and may be a sensor provided in a side slip control system (also referred to as a vehicle stability assist system (VSA)).

[0045] The wheel speed sensor 9 acquires the wheel speed of at least one wheel of the vehicle S. The wheel speed sensor 9 can acquire the wheel speed of the driving wheel and outputs the acquired wheel speed to the control device 17 .

[0046] The external environment recognition device is a device for acquiring information about the surrounding environment of the vehicle S, and includes, for example, a vehicle-mounted camera, radar, laser radar, etc.

[0047] The steering and acceleration / deceleration device 13 performs steering and acceleration / deceleration of the vehicle S. The steering and acceleration / deceleration device 13 includes: a steering device for steering the vehicle S; a driving device for providing driving force to the vehicle S, such as an internal combustion engine or a motor; and a braking device for decelerating the vehicle S.

[0048] The HMI 15 is a device for receiving input from the occupant and providing notifications to the occupant. In this embodiment, the HMI 15 is comprised of a touch panel. If the HMI 15 receives input from the occupant to initiate autonomous driving but the estimated accuracy of the vehicle state is low, the HMI 15 notifies the occupant that autonomous driving is not possible.

[0049] The control device 17 is a so-called microcomputer provided with a processor, RAM, etc., and is connected to the two inertial measurement sensors 5 , 7 , the wheel speed sensor 9 , the external environment recognition device, the steering and acceleration / deceleration device 13 , and the HMI 15 .

[0050] The control device 17 includes a vehicle state estimator 31 (vehicle state estimation unit) that estimates the vehicle state; an abnormality determiner 33 (abnormality determination unit) that determines an abnormality in the primary inertial measurement sensor 5; a state management unit 35 that manages the autonomous driving level of the vehicle S based on input to the HMI 15; an own vehicle position estimation unit 37 that estimates the own vehicle position; and a driving control unit 39 that controls the steering and acceleration / deceleration of the vehicle S so that the vehicle S drives autonomously. The vehicle state estimated by the vehicle state estimator 31 includes the vehicle speed, the time rate of change of the vehicle speed (hereinafter referred to as motion acceleration), and the attitude angle.

[0051] When an instruction to start autonomous driving is received from HMI 15, abnormality determiner 33 determines whether there is an abnormality in main inertial measurement sensor 5. If abnormality determiner 33 determines that there is no abnormality in main inertial measurement sensor 5, state management unit 35 provides an instruction to vehicle position estimation unit 37, causing it to estimate the vehicle position based on the signal from the external environment recognition device and the vehicle state estimated by vehicle state estimator 31 based on the measurement values ​​from main inertial measurement sensor 5 (six-axis inertial measurement sensor). Driving control unit 39 uses the vehicle position estimated by vehicle position estimation unit 37 to control steering and acceleration / deceleration device 13, causing vehicle S to autonomously drive.

[0052] The vehicle control system 3 is further provided with a slip determination device 41 (determination unit) that determines whether the wheel is in a slip state (or a slipping state). The slip determination device 41 includes an anti-lock braking system (ABS) 43 and a traction control system (TCS) 45.

[0053] The anti-lock braking system 43 prevents wheels from stopping (or locking) due to sudden braking, thereby preventing wheel slip. In this embodiment, the anti-lock braking system 43 determines whether a wheel is locked and slipping based on the wheel speed and vehicle velocity. If wheel slip is determined, the anti-lock braking system 43 outputs a flag signal indicating the occurrence of wheel slip to the control device 17, releases the braking force to restore the wheel speed, and then repeatedly maintains and increases the braking pressure to decelerate the vehicle S.

[0054] The traction control system 45 prevents wheel spin during startup or sudden acceleration. In this embodiment, the traction control system 45 determines whether the wheels are spinning and slipping by comparing the wheel speed with the vehicle speed. If the wheels are spinning and slipping, the traction control system 45 outputs a flag signal indicating wheel slippage to the control device 17 and controls the rotational speed of the drive wheels.

[0055] The vehicle state estimation device 1 includes the control device 17 (more specifically, the vehicle state estimator 31) and the slip determination device 41, and estimates the vehicle state including the vehicle speed and attitude angle.

[0056] Next, the vehicle state estimator 31 will be described in detail. The vehicle state estimator 31 calculates estimated values ​​of the vehicle state including vehicle speed, motion acceleration, and attitude angle based on signals from the main inertial measurement sensor 5, the wheel speed sensor 9, and the slip determination device 41, and updates the vehicle state with the calculated estimated values.

[0057] When the vehicle speed is expressed as u(=u x i+u y j+u z k), the motion acceleration a is expressed by the following formula (2).

[0058]

[0059] The kinematic acceleration a is the time variation of the vehicle velocity relative to the acceleration coordinate system and is also known as the relative derivative of the vehicle velocity. Meanwhile, the time variation of the vehicle velocity relative to the fixed coordinate system (du / dt) corresponds to the acceleration G in the fixed coordinate system and is also known as the absolute derivative of the vehicle velocity. The acceleration G and kinematic acceleration conform to the following relationship.

[0060]

[0061] The vehicle state estimator 31 outputs the attitude angle by using the Euler angle (or Tait-Bryan angle). When denoted by , the pitch angle by θ, and the yaw angle by ψ, the attitude angle Ω is expressed by the following formula (4).

[0062] Ω=[φ θ ψ] T (4)

[0063] In the description below, the estimated value of the vehicle speed will be referred to as the estimated vehicle speed v, the estimated value of the motion acceleration will be referred to as the estimated motion acceleration α, the estimated value of the attitude angle will be referred to as the estimated attitude angle Θ, the estimated vehicle speed before updating will be referred to as the pre-updated estimated vehicle speed v0, and the estimated attitude angle before updating will be referred to as the pre-updated estimated attitude angle Θ0.

[0064] The vehicle state estimator 31 (vehicle state estimation unit) includes, as functional units for estimating the vehicle state, an activation determination unit 51, a motion acceleration calculation unit 53, a motion acceleration correction / calculation unit 55, a motion acceleration integrator 57, an attitude angle change rate calculation unit 59 (also referred to as an angular velocity coordinate conversion unit), a gravity term estimation unit 61, an angle decomposition unit 63, an attitude angle change rate correction / calculation unit 65, and an attitude angle change rate integrator 67. These functional units are configured by the processor executing a vehicle state estimation program.

[0065] The activation determination unit 51 sets an observer gain related to speed estimation (hereinafter referred to as acceleration gain K) and an observer gain related to attitude estimation (hereinafter referred to as attitude angle gain K) based on the flag signal calculated by the anti-lock brake system 43 and the flag signal from the traction control system 45. ANG ). The activation determination unit 51 sets the acceleration gain K and the attitude angle gain K ANG Output to the motion acceleration correction / calculation unit 55.

[0066] Note that when any one of the flag signal indicating activation of the anti-lock brake system 43 from the anti-lock brake system 43 and the flag signal indicating activation of the traction control system 45 from the traction control system 45 is input, the activation determination unit 51 determines that the wheel is slipping and sets the acceleration gain K and the attitude angle gain K to the value of the activation determination unit 51. ANG Each of is set to be smaller than the other.

[0067] The motion acceleration calculation unit 53 is configured to receive: the angular velocity ω and the acceleration G obtained by the main inertial measurement sensor 5 sens ; Pre-updated estimated vehicle velocity v0; and pre-updated estimated attitude angle The motion acceleration calculation unit 53 calculates the gravity acceleration in the acceleration coordinate system according to formula (5):

[0068]

[0069] Please note that in formula (5), g represents the magnitude of the acceleration due to gravity (approximately 9.8 m / s 2 ).

[0070] Thereafter, the motion acceleration calculation unit 53 calculates the gravitational acceleration calculated according to formula (5) by The pre-updated estimated vehicle velocity v0, the angular velocity ω and acceleration G obtained by the inertial measurement sensor sens Enter the following formula (6) to calculate the instantaneous motion acceleration α w Thereafter, the motion acceleration calculation unit 53 converts the pre-updated estimated vehicle speed v0 and the instantaneous motion acceleration α w Output to the motion acceleration correction / calculation unit 55.

[0071] α w =G v (θ0,φ0)+G sens -ω×v0 (6)

[0072] According to formula (1) and formula (3), it can be understood that formula (6) is derived from formula (1) and formula (3).

[0073] In addition, the motion acceleration calculation unit 53 calculates the drag acceleration α according to the following formula (7) by using the angular velocity ω acquired by the main inertial measurement sensor 5 and the pre-updated estimated vehicle speed v0: c (also called centripetal acceleration), and will involve acceleration α c Output to the gravity term estimation unit 61.

[0074] α c =ω×v0 (7)

[0075] The motion acceleration correction / calculation unit 55 is configured to receive the wheel speed from the wheel speed sensor 9, the pre-updated estimated vehicle speed v0 from the motion acceleration calculation unit 53, and the motion acceleration α w and the acceleration gain K from the activation determination unit 51 .

[0076] The motion acceleration correction / calculation unit 55 obtains the steady-state vehicle velocity v based on the wheel speed input from the wheel speed sensor 9. meas , the steady-state vehicle speed is an estimate of the vehicle speed. In the case of no wheel slip, the steady-state vehicle speed v meas is essentially matched to the vehicle velocity. However, in the case of wheel slip, the steady-state vehicle velocity v meas Does not match vehicle speed.

[0077] Furthermore, the motion acceleration correction / calculation unit 55 calculates the motion acceleration α byw , pre-updated estimated vehicle speed v0, steady-state vehicle speed v meas The acceleration gain K is input into the following formula (8) to calculate and update the estimated motion acceleration α.

[0078] α=α w -K(v0-v mes ) (8)

[0079] The right side of formula (8) corresponds to using the feedback term (-K(v0-v meas )) for the instantaneous acceleration α w Correction. As can be understood by referring to formula (2), formula (8) is a differential equation with respect to the rate, and formula (8) corresponds to the so-called observer equation with respect to the rate (hereinafter, formula (8) will be referred to as the rate observer equation). In other words, the motion acceleration correction / calculation unit 55 calculates the estimated motion acceleration α by using the rate observer equation (formula (8)), which is a differential equation with respect to the rate, in which the instantaneous motion acceleration α is corrected using the feedback term. w .

[0080] The motion acceleration correction / calculation unit 55 outputs the calculated estimated motion acceleration α to the gravity term estimation unit 61 and the own vehicle position estimation unit 37 .

[0081] The motion acceleration integrator 57 is configured to receive the estimated motion acceleration α from the motion acceleration correction / calculation unit 55. The motion acceleration integrator 57 time-integrates the estimated motion acceleration α and updates the estimated vehicle speed v with a value (∫αdt) obtained by the time integration.

[0082] Note that, when performing time integration on the estimated motion acceleration α, the motion acceleration integrator 57 may ignore the time variation of the unit vectors i, j, k and integrate the x component, y component, and z component of the estimated motion acceleration α separately to obtain the estimated vehicle velocity v. Specifically, for example, the motion acceleration integrator 57 may utilize the pre-updated estimated vehicle velocity v0 (assuming that its x, y, and z components are v0x, v0y, and v0z, respectively, when calculating) and the estimated motion acceleration α (assuming that its x, y, and z components are α, respectively, when calculating) by using the so-called Euler method. x , α y , α z More specifically, the motion acceleration integrator 57 can calculate (v 0y +α x Δt)i+(v 0y +α y Δt)j+(v 0z +α zΔt)k (note that i, j, k are unit vectors in the x, y, and z directions, respectively, when calculating the estimated vehicle speed, and Δt is the control interval of the estimation calculation, more specifically, the time elapsed from the calculation of the pre-updated estimated vehicle speed v0), and the calculated value is output as the estimated vehicle speed v.

[0083] The motion acceleration integrator 57 outputs the updated estimated vehicle speed v to the motion acceleration calculation unit 53 and the travel control unit 39 .

[0084] The attitude angle change rate calculation unit 59 is configured to receive the pre-updated attitude angle estimate (pre-updated estimated attitude angle θ0) and the angular velocity ω acquired by the main inertial measurement sensor 5. The attitude angle change rate calculation unit 59 inputs the angular velocity ω and the pre-updated estimated attitude angle θ0 into the following formula (9) to calculate the attitude angle change rate (This is the time change rate of the attitude angle) and outputs it to the attitude angle change rate correction / calculation unit 65.

[0085]

[0086] Formula (9) shows that the attitude angle change rate This corresponds to the attitude angle change rate predicted by performing coordinate conversion of the angular velocity ω.

[0087] The gravity term estimation unit 61 is configured to receive the acceleration G acquired by the inertial measurement sensor. sens , the estimated motion acceleration α updated by the motion acceleration correction / calculation unit 55, and the involved acceleration α from the motion acceleration calculation unit 53 c The gravity term estimation unit 61 converts the acceleration G sens , updated estimated motion acceleration α and implicated acceleration α c Enter the following formula (10) to calculate the gravity term G std and outputs it to the angle decomposition unit 63.

[0088] G std =ɑ+ɑ c -G sens (=-(G sens -ɑ-ɑ c )) (10)

[0089] Formula (10) shows that the gravity term G std Corresponds to the value obtained by the following operation: From the acceleration G acquired by the inertial measurement sensor sens Subtract the estimated motion acceleration α0 and the implicated acceleration α c(=ω×v0), and considering that the gravitational acceleration is calculated based on the inertial force, the subtraction result is inverted.

[0090] Gravity term G std is input from the gravity term estimation unit 61 to the angle resolution unit 63. The angle resolution unit 63 obtains the gravity term G based on the following formula (11): std Quantity g estX 、g estY and g estZ .

[0091]

[0092] Then, the angle decomposition unit 63 converts the gravity term G std Input into the following formula (12) to obtain the steady-state attitude angle Θ grav and the steady-state attitude angle Θ grav Output to the attitude angle change rate correction / calculation unit 65 (here, g is about 9.8m / s 2 ).

[0093]

[0094] Note that in formula (12), there is no gravity term G std Calculate the yaw angle ψ, only the roll angle is calculated and the pitch angle θ. By referring to formula (5), it can be understood that formulas (11) and (12) show that the steady-state attitude angle θ grav The direction of gravity acceleration is estimated by using the gravity term G std ) Estimated attitude angle vertically downward.

[0095] The attitude angle change rate correction / calculation unit 65 is configured to receive the steady-state attitude angle θ from the angle resolution unit 63. grav and the attitude angle gain K for attitude estimation from the activation determination unit 51 ANG By using the steady-state attitude angle θ based on the input from the angle decomposition unit 63 grav , About the attitude angle gain K of attitude estimation ANG and the following formula (13) of the pre-updated estimated attitude angle Θ0, the attitude angle change rate correction / calculation unit 65 obtains the time change rate ΔΘ of the estimated attitude angle (i.e., the time derivative of the estimated attitude angle) and outputs it to the attitude angle change rate integrator 67.

[0096] ΔΘ=ΔΘ T (θ0,φ0,ω)-K ANG (Θ0-Θ grav ) (13)

[0097] The right side of formula (13) corresponds to using the feedback term (-K ANG (Θ0-Θ grav ) for attitude angle change rate Correction. Formula (13) is a differential equation about the attitude angle and corresponds to the so-called observer equation about the attitude angle (hereinafter, formula (13) will be referred to as the attitude angle observer equation). In other words, the attitude angle change rate correction / calculation unit 65 calculates the estimated attitude angle time change rate by using the attitude angle observer equation (formula (13)), wherein the attitude angle change rate is corrected using the feedback term

[0098] Furthermore, the attitude angle change rate correction / calculation unit 65 combines the pre-updated estimated attitude angle θ0 with the gravity term G std Estimated steady-state attitude angle Θ grav Output to the abnormality determiner 33.

[0099] The attitude angle change rate integrator 67 is configured to receive the time change rate ΔΘ of the estimated attitude angle. The attitude angle change rate integrator 67 time-integrates the time change rate ΔΘ of the estimated attitude angle and updates the estimated attitude angle Θ with the value obtained by the time integration (ie, ∫ΔΘdt).

[0100] More specifically, the attitude angle change rate integrator 67 can calculate the value of the time integral by adding the product of the time Δt required before updating and the time change rate ΔΘ of the estimated attitude angle to the pre-updated estimated attitude angle Θ0, and update the estimated attitude angle Θ with the value of the time integral (Θ0+ΔΘΔt).

[0101] The attitude angle change rate integrator 67 outputs the updated estimated attitude angle θ to the motion acceleration calculation unit 53 and the travel control unit 39.

[0102] Next, the abnormality determiner 33 will be described. The abnormality determiner 33 executes an abnormality determination program so as to always perform an abnormality determination when the vehicle S autonomously travels. Figure 3 The abnormality determination processing shown in is executed to execute the abnormality determination method for determining whether or not an abnormality exists in the main inertial measurement sensor 5. Figure 3 The flowchart of FIG. 1 describes the abnormality determination process performed by the abnormality determiner 33 .

[0103] In the first step ST1 of the abnormality determination process, the abnormality determiner 33 determines the acceleration G acquired by the primary inertial measurement sensor 5. sens The x component G sensx Is it consistent with the acceleration G' in the x direction obtained by the auxiliary inertial measurement sensor 7? sensxThe abnormality determiner 33 can determine the acceleration G obtained by the main inertial measurement sensor 5 by performing a correlation comparison between the two. sens The x component G sensx Is it consistent with the acceleration G' in the x direction obtained by the auxiliary inertial measurement sensor 7? sensx In addition, when the difference between the two is less than or equal to a prescribed threshold, the abnormality determiner 33 may determine that the acceleration G obtained by the main inertial measurement sensor 5 is sens The x component G sensx The acceleration G′ in the x direction obtained by the auxiliary inertial measurement sensor 7 sensx When determining that the two values ​​match each other, the abnormality determiner 33 executes step ST2 , and when determining that they do not match, executes step ST3 .

[0104] In step ST2, the abnormality determiner 33 determines the acceleration G acquired by the primary inertial measurement sensor 5. sens The y component G sensy Is it consistent with the acceleration G' in the y direction obtained by the auxiliary inertial measurement sensor 7? sensy The abnormality determiner 33 can determine the acceleration G obtained by the main inertial measurement sensor 5 by performing a correlation comparison between the two. sens The y component G sensy Is it consistent with the acceleration G' in the y direction obtained by the auxiliary inertial measurement sensor 7? sensy When the difference between the two is less than or equal to the prescribed threshold, the abnormality determiner 33 can determine that the acceleration G obtained by the main inertial measurement sensor 5 is sens The y component G sensy The acceleration G′ in the y direction obtained by the auxiliary inertial measurement sensor 7 sensy When determining that the two values ​​match each other, the abnormality determiner 33 executes step ST4, and executes step ST3 when determining that they do not match.

[0105] In step ST3 , the abnormality determiner 33 sets a flag indicating whether the main inertial measurement sensor 5 has an abnormality (sensor abnormality flag) to a value indicating the presence of an abnormality (eg, 1). After completing the setting, the abnormality determiner 33 ends the abnormality determination process.

[0106] In step ST4 , the abnormality determiner 33 determines the z component ω of the angular velocity ω acquired by the primary inertial measurement sensor 5 . z Is it consistent with the angular velocity ω' about the z direction obtained by the auxiliary inertial measurement sensor 7? z The abnormality determiner 33 can determine ω by performing a correlation comparison between the two. z Is it related to ω' zIn addition, when the difference between the two is less than or equal to the prescribed threshold, the abnormality determiner 33 can determine ω z With ω' z Match. The abnormality determiner 33 executes step ST5 when determining that the two values ​​match each other, and executes step ST3 when determining that they do not match.

[0107] In step ST5, the abnormality determiner 33 determines whether the x and y components of the pre-updated estimated attitude angle θ0 output from the vehicle state estimator 31 (more specifically, from the attitude angle change rate integrator 67) are respectively different from the steady-state attitude angle θ grav The x and y components of the two pairs of corresponding components match. Preferably, the abnormality determiner 33 calculates the difference between each pair of the two pairs of corresponding components as an estimated error, and when the estimated error of each pair is less than or equal to a corresponding prescribed threshold, determines that the corresponding components of each pair match each other. When it is determined that the corresponding components in the two pairs match each other, the abnormality determiner 33 executes step ST6, and when at least one of the estimated error between the x components and the estimated error between the y components is greater than the corresponding threshold, executes step ST3.

[0108] In step ST6, the abnormality determiner 33 sets the sensor abnormality flag to a value (eg, 0) indicating that the sensor is normal (no abnormality), and outputs the sensor abnormality flag to the state management unit 35. After the output is completed, the abnormality determiner 33 ends the abnormality determination process.

[0109] When the sensor abnormality flag input from the abnormality determiner 33 has a value indicating that the sensor is normal, the state management unit 35 allows the vehicle S to travel autonomously. On the other hand, when the sensor abnormality flag has a value indicating that the sensor has an abnormality, the state management unit 35 prevents the vehicle S from traveling autonomously. More specifically, when the sensor abnormality flag has a value indicating that the sensor has an abnormality, the state management unit 35 does not accept input to the HMI 15 for selecting autonomous travel of the vehicle S. Furthermore, if the sensor abnormality flag having a value indicating that the sensor has an abnormality is input during autonomous travel of the vehicle S, the state management unit 35 causes the HMI 15 to display a display indicating that the sensor has an abnormality. Furthermore, the state management unit 35 preferably immediately stops the autonomous travel of the vehicle S and transitions the vehicle S to a manual driving state, in which the vehicle S travels according to the occupant's driving operation.

[0110] Next, the operation of the vehicle state estimation device 1 configured as above will be described.

[0111] When the flag signal indicating activation of the anti-lock braking system 43 is not output from the anti-lock braking system 43, and the flag signal indicating activation of the traction control system 45 is not output from the traction control system 45 (i.e., when the wheels are not slipping), the activation determination unit 51 sets the acceleration gain K and the attitude angle gain K to the value of the activation determination unit 51. ANG Set to a value sufficiently larger than that when any flag signal is output.

[0112] The vehicle state estimator 31 calculates the estimated vehicle speed according to formula (8). Since the left side of formula (8) corresponds to the motion acceleration (i.e., the derivative of the vehicle speed), formula (8) corresponds to the feedback term (-K(v0-v meas )) is added to the observer equation in the differential equation regarding the vehicle velocity (Formula (6), hereinafter referred to as the acceleration equation). When the activation determination unit 51 sets the acceleration gain K to a sufficiently large value, the vehicle state estimator 31 determines to estimate the vehicle velocity so that the feedback term (-K(v0-v meas That is, the vehicle state estimator 31 determines that the estimated vehicle speed is a value close to the steady-state vehicle speed (the contribution of the steady-state vehicle speed is higher than the contribution of the instantaneous vehicle speed obtained by numerical integration of the right side of the acceleration equation).

[0113] The vehicle state estimator 31 calculates the estimated attitude angle according to formula (13). Since the left side of formula (13) corresponds to the derivative of the attitude angle, formula (13) corresponds to the feedback term (-K ANG (Θ0-Θ grav )) is added to the differential equation for the attitude angle (ΔΘ=ΔΘ T , hereinafter referred to as the attitude angle equation) in the observer equation. When the activation determination unit 51 sets the attitude angle gain K ANG When set to a sufficiently large value, the vehicle state estimator 31 determines the estimated attitude angle so that the feedback term (-K ANG (Θ0-Θ grav )) is close to zero. That is, the vehicle state estimator 31 determines that the estimated attitude angle is close to the steady-state attitude angle θ grav The value of the steady-state attitude angle Θ grav The contribution of is higher than the contribution of the instantaneous attitude angle obtained by numerical integration of the right side of the attitude angle equation).

[0114] When a flag signal indicating that the anti-lock braking system 43 is activated is output from the anti-lock braking system 43 and / or a flag signal indicating that the traction control system 45 is activated is output from the traction control system 45 (i.e., when the wheels are slipping), the activation determination unit 51 adjusts the acceleration gain K and the attitude angle gain K to the value of the activation determination unit 51. ANG Set to a sufficiently small value.

[0115] When the activation determination unit 51 sets the acceleration gain K to a sufficiently small value, the vehicle state estimator 31 determines the estimated vehicle speed to be a value close to the instantaneous vehicle speed obtained by numerical integration of the right side of the acceleration equation (the contribution of the instantaneous vehicle speed is higher than that of the steady-state vehicle speed). ANG When set to a sufficiently small value, the vehicle state estimator 31 determines the estimated attitude angle to be a value close to the instantaneous attitude angle obtained by numerical integration of the right side of the attitude angle equation (the contribution of the instantaneous attitude angle is higher than that of the steady-state attitude angle).

[0116] Next, the effects of the vehicle state estimator 31 configured as above will be described.

[0117] When the wheels are not slipping (i.e. not in a slipping state), the vehicle speed obtained based on the wheel speed is close to the true value. On the other hand, when the wheels are in a slipping state, the vehicle speed obtained based on the wheel speed is far from the true value, and the error becomes larger.

[0118] When the wheels are not slipping, Figure 4A As shown in FIG, the estimated vehicle speed (estimated value of the vehicle speed) (two-dot chain line) is determined to be close to the steady-state vehicle speed value (dashed line) obtained by wheel speed sensor 9. On the other hand, the instantaneous vehicle speed (single-dot chain line) obtained by numerically integrating the right side of the acceleration equation includes errors caused by numerical integration. Therefore, by determining the estimated vehicle speed to be a value close to the steady-state vehicle speed (i.e., a value closer to the steady-state vehicle speed than to the instantaneous vehicle speed), the estimated vehicle speed can be made closer to the true value (solid line) compared to the case where the estimated vehicle speed is determined to be a value close to the instantaneous vehicle speed, thereby improving the estimation accuracy of the vehicle speed.

[0119] In addition, when the wheels are not slipping, since the vehicle rate obtained based on the wheel speed is close to the true value, and the instantaneous attitude angle obtained by the numerical integration of the right side of the attitude angle equation includes the error caused by numerical integration, the steady-state attitude angle calculated based on the wheel speed, the acceleration obtained by the inertial measurement sensor, etc. is closer to the true value than the instantaneous attitude angle.

[0120] Therefore, when the wheel is not slipping, the estimated attitude angle (the estimated value of the attitude angle) is determined to be close to the steady-state attitude angle (i.e., a value closer to the steady-state attitude angle than to the instantaneous attitude angle). Therefore, the estimation accuracy can be improved compared to the case where the estimated attitude angle is determined to be close to the instantaneous attitude angle.

[0121] On the other hand, when the wheels are slipping (i.e. in a skidding state), if Figure 4BAs shown in FIG, the estimated vehicle speed (estimated value of the vehicle speed) (two-dot chain line) is determined to be a value close to the instantaneous vehicle speed (single-dot chain line) obtained by numerical integration of the right side of the acceleration equation (i.e., a value closer to the instantaneous vehicle speed than to the steady-state vehicle speed). Therefore, compared to a case where the estimated value of the vehicle speed is determined to be a value close to the steady-state vehicle speed (dashed line), the estimated vehicle speed can be made closer to the true value (solid line), thereby improving the measurement accuracy of the vehicle speed.

[0122] When the wheel is slipping, the instantaneous attitude angle is closer to the true value than the steady-state attitude angle calculated based on the wheel speed. When the wheel is slipping, the estimated attitude angle is determined to be a value close to the instantaneous attitude angle (i.e., a value closer to the instantaneous attitude angle than to the steady-state attitude angle). Therefore, the attitude angle measurement accuracy can be improved compared to the case where the estimated attitude angle is determined to be a value close to the steady-state attitude angle.

[0123] like Figure 4A As shown in , the instantaneous vehicle speed may change over time to deviate from the true value of the vehicle speed. In the present embodiment, the acceleration gain K is large enough, and when the wheel is not slipping, the estimated vehicle speed is calculated to be substantially equal to the steady-state vehicle speed acquired by the wheel speed sensor 9. When the wheel begins to slip, the acceleration gain K changes, and the estimated vehicle speed is calculated to be close to the instantaneous vehicle speed obtained by numerical integration, with the estimated vehicle speed being the initial value when the wheel begins to slip. Therefore, the lower limit (also referred to as the lower end) of the integration interval of the numerical integration used to calculate the instantaneous vehicle speed can be set to the time when slipping begins. Therefore, compared with the case where the lower limit of the integration interval is set to the time when the vehicle begins to move, the integration interval used to calculate the instantaneous vehicle speed can be shortened, and therefore, the error of the estimated vehicle speed during slipping (i.e., the instantaneous vehicle speed) can be reduced.

[0124] The mass of vehicle S varies depending on the usage state of vehicle S, such as the amount of load, and the friction coefficient between the road surface and the wheels (tires) also varies significantly depending on the road surface conditions. Therefore, if the equation of motion of vehicle S is established using parameters that vary depending on tire parameters, such as those representing the cornering power coefficient, which have uncertainty, these parameters must be changed to account for the usage state and road surface conditions, making it difficult to estimate the vehicle state.

[0125] In this embodiment, as shown in Formula (8) and Formula (13), neither the velocity observer equation nor the attitude angle observer equation includes mass and friction coefficient. Therefore, the vehicle velocity and attitude angle can be calculated without depending on parameters with uncertainty, such as the mass and friction coefficient of the vehicle S. This allows estimation of the vehicle state to be independent of the vehicle S's usage status or road conditions.

[0126] By changing the acceleration gain K and attitude angle gain K ANG , it is possible to determine the estimated vehicle speed (estimated attitude angle) to be close to the steady-state vehicle speed (steady-state attitude angle) when the wheels are not slipping, and to determine it to be close to the instantaneous vehicle speed (instantaneous attitude angle) when the wheels are slipping. In addition, because the estimated vehicle speed (estimated attitude angle) is obtained by integrating and updating the observer equation, the instantaneous characteristics and steady-state characteristics can be integrated, thereby determining the estimated vehicle speed (estimated attitude angle) as the most likely value within the entire steady-state / unsteady-state motion range.

[0127] In the above embodiment, based on the activation of the anti-lock braking system 43 or the traction control system 45, it is determined whether the wheel is slipping, and the acceleration gain K and the attitude angle gain K are set accordingly. ANG In this way, activation of the anti-lock braking system 43 or the traction control system 45 is used to determine whether a wheel is in a slipping state, from which it can be easily determined.

[0128] Next, the operation and effects of the abnormality determiner 33 will be described.

[0129] When wheels slip, the vehicle velocity obtained based on the wheel speed differs from the true value. Therefore, the vehicle's fore-and-aft acceleration obtained by main inertial measurement sensor 5 (six-axis inertial measurement sensor) and the fore-and-aft acceleration obtained based on the wheel speed may deviate from each other. Consequently, it is difficult to determine an abnormality in main inertial measurement sensor 5 by comparing the fore-and-aft acceleration obtained by main inertial measurement sensor 5 with the fore-and-aft acceleration obtained by wheel speed sensor 9.

[0130] In step ST1, abnormality determiner 33 compares the vehicle's front-to-rear acceleration acquired by primary inertial measurement sensor 5 (six-axis inertial measurement sensor) with the vehicle's front-to-rear acceleration acquired by auxiliary inertial measurement sensor 7 (three-axis inertial measurement sensor). If these values ​​do not match, abnormality is determined to exist in primary inertial measurement sensor 5 (six-axis inertial measurement sensor). Therefore, compared to using front-to-rear acceleration acquired by wheel speed sensor 9, even in the presence of wheel slip, abnormality in primary inertial measurement sensor 5 can be accurately determined when detecting front-to-rear acceleration. Consequently, it is possible to accurately determine whether the vehicle S's forward movement can be accurately acquired, that is, whether its own position can be accurately assessed.

[0131] In step ST2, the abnormality determiner 33 compares the acceleration in the lateral direction acquired by the main inertial measurement sensor 5 with the acceleration of the vehicle in the lateral direction acquired by the auxiliary inertial measurement sensor 7, and when they do not match, determines that an abnormality exists in the main inertial measurement sensor 5. In addition, in step ST3, the abnormality determiner 33 determines the z component ω of the angular velocity ω (i.e., yaw rate) acquired by the main inertial measurement sensor 5. z Is it consistent with the angular velocity ω' around the z axis obtained by the auxiliary inertial measurement sensor 7? z (i.e. yaw rate) matching.

[0132] In this manner, abnormality determiner 33 compares the front-rear acceleration, lateral acceleration, and yaw rate acquired by primary inertial measurement sensor 5 with the corresponding values ​​acquired by auxiliary inertial measurement sensor 7 to determine whether an abnormality exists. Thus, a mutual monitoring mechanism between the two sensors can be configured, and overall costs can be reduced by using a 3-axis inertial measurement sensor, which is less expensive than a 6-axis inertial measurement sensor, compared to using two 6-axis inertial measurement sensors.

[0133] In addition, since the abnormality determiner 33 compares the acceleration in the fore-aft direction, the acceleration in the lateral direction and the yaw rate obtained by the main inertial measurement sensor 5 with the corresponding values ​​obtained by the auxiliary inertial measurement sensor 7, it is able to more reliably detect abnormalities in the acceleration in the fore-aft direction, the acceleration in the lateral direction and the yaw rate. When an abnormality occurs, such an abnormality may cause a large error in the estimated value of its own position.

[0134] In step ST5, the abnormality determiner 33 calculates the difference between the estimated value of the attitude angle (i.e., the estimated attitude angle θ0) obtained by numerically integrating the attitude angle equation (Formula (13)) and the steady-state attitude angle θ grav The difference between the two values ​​is considered as the estimated error. Since the estimated error becomes too large when an abnormality occurs in the 6-axis inertial measurement sensor, the abnormality determiner 33 can determine whether there is an abnormality in the 6-axis inertial measurement sensor by using the estimated error.

[0135] More specifically, in step ST5, the abnormality determiner 33 calculates the x component of the estimated attitude angle Θ0 and the steady-state attitude angle Θ grav The difference between the x component of the estimated attitude angle Θ0 and the y component of the steady-state attitude angle Θ grav , and determines whether each calculated difference is less than or equal to a corresponding threshold value. Thus, abnormality determiner 33 can detect abnormalities in the roll direction and pitch direction of main inertial measurement sensor 5 (six-axis inertial measurement sensor), which were not evaluated in steps ST2 and ST4.

[0136] A specific embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment and can be modified or altered in various ways.

[0137] In the above embodiment, the slip determination device 41 is provided with an anti-lock braking system 43 and a traction control system 45, but the present invention is not limited to this embodiment. For example, the slip determination device 41 may be provided with a vehicle stability assist system (VSA) (also known as a lateral slip control system) and determine that the wheel is in a slipping state when, for example, control is performed to suppress lateral slip of the wheel during cornering. In addition, the slip determination device 41 may be provided with a steering angle sensor and determine that the wheel is in a slipping state when the time rate of change of the steering angle detected by the steering angle sensor is greater than or equal to a specified threshold. In addition, the slipping state may include: a state in which the wheel may be in a slipping state, a state in which the wheel may be in a slipping state depending on the road surface conditions, and / or a state immediately before entering a slipping state.

[0138] In the above embodiment, the velocity of the position of the main inertial measurement sensor 5 (six-axis inertial measurement sensor) is calculated, but the present invention is not limited to this embodiment. For example, a configuration may be made so that the velocity of the prescribed position of the vehicle S is estimated by converting the estimated speed obtained by the main inertial measurement sensor 5 using the following formula (14).

[0139] v=v0+ω×L (14)

[0140] Note that in formula (14), v represents the rate after conversion, v0 represents the rate before conversion, ω represents the angular velocity detected by the main inertial measurement sensor 5, and L represents a vector whose origin is located at the position where the main inertial measurement sensor 5 is set and whose end point is located at the position of the vehicle whose rate is to be estimated.

[0141] In the above embodiment, the abnormality determiner 33 determines the attitude angle estimated value (ie, estimated attitude angle θ0) obtained based on the attitude angle equation and the steady-state attitude angle θ grav The estimated error in ST5 is calculated by calculating the difference between the values ​​of ...

Claims

1. A vehicle state estimation device configured to be installed in a vehicle to estimate a vehicle state including a vehicle speed, wherein: The vehicle is provided with an inertial measurement sensor for acquiring acceleration and angular velocity and a wheel speed sensor for acquiring wheel speed, and the vehicle state estimation device includes: a vehicle state estimation unit that estimates the vehicle state based on the acceleration and angular velocity acquired by the inertial measurement sensor and the wheel speed acquired by the wheel speed sensor; and a determining unit, the determining unit determining whether the wheel is in a slipping state, wherein the vehicle state estimation unit estimates a steady-state vehicle velocity based on the wheel velocity and calculates an instantaneous vehicle velocity by time integration based on the acceleration and the angular velocity, The vehicle state estimation unit determines that the estimated value of the vehicle speed is close to the instantaneous vehicle speed when the wheel is in the slipping state, and determines that the estimated value of the vehicle speed is close to the steady-state vehicle speed when the wheel is not in the slipping state, and The vehicle state includes the attitude angle of the vehicle, The vehicle state estimation unit calculates a steady-state attitude angle based on the gravity direction estimated using the wheel speed and the acceleration acquired by the inertial measurement sensor, and calculates an instantaneous attitude angle by time-integrating the angular velocity acquired by the inertial measurement sensor, and When the wheel is in the slipping state, the vehicle state estimation unit determines that the estimated value of the attitude angle is close to the instantaneous attitude angle, and when the wheel is not in the slipping state, the vehicle state estimation unit determines that the estimated value of the attitude angle is close to the steady-state attitude angle, The vehicle state estimation unit estimates the vehicle speed and the attitude angle based on the following equation: a rate observer equation indicating that a relative derivative of the vehicle rate is equal to a sum of gravitational acceleration, acceleration acquired by the inertial measurement sensor, a vector product of an estimate of the vehicle rate and an angular velocity acquired by the inertial measurement sensor, and a feedback term for providing feedback at a prescribed acceleration gain so that the vehicle rate approaches the steady-state vehicle rate; and an attitude angle observation equation, wherein the attitude angle observation equation indicates that the time derivative of the attitude angle is equal to the sum of the instantaneous attitude angle and a feedback term for providing feedback at a prescribed attitude angle gain so that the attitude angle approaches the steady-state attitude angle, and The vehicle state estimation unit makes the acceleration gain and the attitude angle gain smaller when the wheel is in the slipping state than when the wheel is not in the slipping state.

2. The vehicle state estimation device according to claim 1, wherein: The determination unit includes at least one of an anti-lock braking system and a traction control system.

3. A vehicle state estimation method for estimating a vehicle state including a vehicle velocity of a vehicle, the vehicle being provided with an inertial measurement sensor for acquiring acceleration and angular velocity and a wheel speed sensor for acquiring wheel speed, the vehicle state estimation method comprising the following steps: Determine whether the wheels are in a slipping state; estimating a steady-state vehicle velocity based on the wheel speed; calculating an instantaneous vehicle velocity based on the acceleration and the angular velocity by time integration; When the wheel is in the slipping state, determining that the estimated value of the vehicle speed is close to the instantaneous vehicle speed, and when the wheel is not in the slipping state, determining that the estimated value of the vehicle speed is close to the steady-state vehicle speed, and The vehicle state includes the attitude angle of the vehicle, The vehicle state estimation method calculates a steady-state attitude angle based on the gravity direction estimated using the wheel speed and the acceleration acquired by the inertial measurement sensor, and calculates an instantaneous attitude angle by time-integrating the angular velocity acquired by the inertial measurement sensor; and When the wheel is in the slipping state, the vehicle state estimation method determines that the estimated value of the attitude angle is close to the instantaneous attitude angle, and when the wheel is not in the slipping state, the vehicle state estimation method determines that the estimated value of the attitude angle is close to the steady-state attitude angle, The vehicle state estimation method estimates the vehicle speed and the attitude angle based on the following equations: a rate observer equation indicating that a relative derivative of the vehicle rate is equal to a sum of gravitational acceleration, acceleration acquired by the inertial measurement sensor, a vector product of an estimated value of the vehicle rate and an angular velocity acquired by the inertial measurement sensor, and a feedback term for providing feedback at a prescribed acceleration gain so that the vehicle rate approaches the steady-state vehicle rate; as well as an attitude angle observation equation, wherein the attitude angle observation equation indicates that the time derivative of the attitude angle is equal to the sum of the instantaneous attitude angle and a feedback term for providing feedback at a prescribed attitude angle gain so that the attitude angle approaches the steady-state attitude angle, and The vehicle state estimation method makes the acceleration gain and the attitude angle gain smaller when the wheel is in the slipping state than when the wheel is not in the slipping state.

4. A non-transitory computer-readable storage medium comprising a stored program, wherein: The stored program performs the method of claim 3 when executed by a processor.

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